A discussion on the Proterozoic stratigraphy framework in the basement of eastern section of the Mid Qilian Massif

It is generally considered that the basement of the eastern part of Mid Qilian Massif consists of three stratigraphic sequences that are separated by parallel unconformable boundaries:the Paleoproterozoic Huangyuan Group,Mesoproterozoic Huangzhong Group and Huashishan Group.However,recent study suggest that(1)The Huashishan Group unconformably overlies the Huangyuan Group at angle,and paleontological data suggests that the Huashishan Group represents a stable sedimentary cover of Sinian to Cambrian age,rather than basement.(2)The Huangyuan Group and Huangzhong Group were formed in the same tectonic cycle and should be combined as Huangyuan Group.